I think a little documented issue with Arcade CRT's is "Dot Pitch". For example, the original monitors on a Pac Man, is probably using a much lower dot pitch than anything that replaced it years later... and the resulting look, is quite different.
The shadowmasks have gotten smaller and smaller over the years, and so the black lines of the masks being thinner do not obscure or blur the image as much. Phosphor glow also does not bleed as much, maybe due to the guns being more accurate.. or merely the shadowmask lined being thinner.
The argument is easily seen on typical tube tvs to a larger degree. Even at low resolution, my sony 34" widescreen CRT hdtv is way too clean looking. No bleed, color blending, blur..etc. Even the old 27" panasonic with 480i capability looks different than the old arcade monitors. Certainly looks more authentic than the sony, but still not arcade accurate by any means.
The HLSL feature is a very welcome feature. However, its labels and settings are hard to really figure out. Theres no real standard set of semi-accurate presets included... yet. And the people working on their own filters, seem to be just making something that looks good to them, rather than trying to compare an actual arcade monitor on the spot, and match that result closely as possible. (nor using monitor spec data, such as dot pitch... color output ranges, etc)
Hopefully in time that will change. The other thing about the filter... Im not sure it calculates things like color bleeding and staggered pixel effects. An example, is that some games used a diagonally staggered pattern of black lines. When viewed in mame, you can see the pattern... however, when viewed on a real arcade monitor... you see what appears to be a darker transparent (see-through) graphic. (such as a floating power bar, a characters shadow, etc)
I believe there were also games that used crt refresh timing to create certain effects as well. I think I read something about a trick where they would draw between a scanline.